This invention relates to a variable thresholding circuit for converting analog signals into digital signals, and more particularly, to a variable thresholding circuit in which a threshold level for converting analog signals such as image signals into binary signals is changed due to the level of the analog signals.
In the field of pattern recognition, image signals from an image pick-up device such as an industrial TV camera have been converted into binary signals in accordance with a constant threshold level. In this case, binary signals having stability for a long period of time have not been obtained since the gains and the DC levels of the image signals vary at a relatively slow speed due to the variations of temperature and brightness.